FurnacesOil
Conforto KHM-G3-*078-03 Furnace Manual
Setup, everyday use, maintenance and troubleshooting for the 87% AFUE oil furnace, with verified specifications.
- AFUE87%
- FuelFuel oil
- ENERGY STAR regionAll regions
- Example yearly oil use415 gal
About the Conforto KHM-G3-*078-03
This guide covers the Conforto KHM-G3-*078-03, an 87% AFUE oil furnace on the ENERGY STAR certified furnace list.
Its AFUE of 87% means that over a typical heating season about 87% of the oil it burns ends up as heat in your home, while roughly 13% is lost through the vent and in cycling losses. Like most oil furnaces it is a non-condensing design, so it vents hot flue gases through a lined chimney or a listed power-vent system and does not produce a condensate stream.
ENERGY STAR lists this furnace as certified for all regions, meaning it meets the program's stricter requirements for northern states — where furnaces run many more hours each year — as well as the southern criteria.
Specifications
| Brand | Conforto |
|---|---|
| Model number | KHM-G3-*078-03* |
| Fuel category | Oil |
| AFUE (heating efficiency) | 87.0% |
| Fuel type | Fuel oil |
| Condensing design | No |
| ENERGY STAR certified in | All regions |
Safety information
- Install UL-listed carbon monoxide (CO) alarms on every level of the home and outside each sleeping area. Test them monthly and replace them at the end of the life printed on the alarm.
- If you smell oil fumes or see smoke or soot around the furnace, turn it off at the emergency switch and call a qualified oil-heat technician.
- Never press the burner reset button more than once. Repeated resets can pump unburned oil into the combustion chamber, which can ignite violently (a "puffback") when the burner finally lights.
- Furnace installation, gas or oil piping, venting and electrical work must be done by a licensed heating contractor following the manufacturer's instructions and local codes. Most jurisdictions require a permit and inspection.
- Never store gasoline, paint thinner, solvents, aerosols or other flammable products near the furnace, and keep the area around it clear of storage.
- Do not operate the furnace with the burner or blower access doors removed. The doors seal the combustion area, and a door safety switch cuts power when the blower door is off.
- Turn off power at the furnace service switch or breaker before changing the filter or opening any panel.
Installation and first-time setup
Proper installation determines whether the Conforto KHM-G3-*078-03 delivers its rated efficiency safely. Use the checklist below when reviewing quotes and when the work is finished.
- Size it to the house
Ask for an ACCA Manual J heat-loss calculation rather than matching the old furnace's size. Oversized furnaces short-cycle, heat unevenly and wear out sooner. The calculation also tells the contractor how much airflow the ductwork needs to deliver.
- Location and clearances
Install the furnace in a location and orientation the installation manual allows, with the listed clearances to combustibles and enough room in front for service. Garage installations need protection from vehicle impact and must follow local code for ignition sources.
- Venting and draft
Oil furnaces vent into a properly sized, lined masonry or factory-built chimney with a barometric draft regulator, or through a power venter listed for the furnace. The installer should measure draft over the fire and at the breech.
- Oil supply
The oil tank, supply line and filter must meet NFPA 31 and local code, with the line protected from damage and a fire-safety (fusible) valve where required.
- Ductwork and airflow
The contractor should measure total external static pressure, set the blower speed taps for heating (and cooling, if an air conditioner shares the blower) and confirm that the temperature rise across the furnace is within the range on the rating plate.
- Commissioning
Ask for a written start-up report with nozzle size, pump pressure, draft, smoke test, CO and combustion-efficiency readings.
Using your furnace
Thermostat settings
Furnaces recover quickly, so thermostat setbacks save fuel. The U.S. Department of Energy estimates you can save up to 10% a year on heating by turning the thermostat back 7–10 °F for eight hours a day, such as overnight or while you are at work.
What a normal heating cycle looks like
On a call for heat the burner motor starts, the ignitor lights the oil spray and the flame is proven by a light-sensing cad cell. The blower starts once the heat exchanger warms up and keeps running for a short time after the burner stops. A steady, even burner roar is normal; rumbling, pulsing or smoke is not.
Fan setting
Leave the thermostat fan on "Auto" for the lowest electricity use: the blower runs only while the furnace is heating. "On" circulates air continuously, which can even out temperatures and improve filtration but uses more electricity and can feel drafty in winter.
Care and maintenance
| When | What to do |
|---|---|
| Every 1–3 months | Check the air filter and replace it when dirty (1 in. filters usually monthly to quarterly; 4–5 in. media filters every 6–12 months). A clogged filter is the most common cause of overheating and safety shutdowns. |
| Every month | Test CO and smoke alarms. During the heating season, glance at the furnace and listen for unusual noises. |
| Every year, before the heating season | Professional oil-burner tune-up: replace the nozzle and oil filter, clean the pump strainer, adjust electrodes, clean the heat exchanger and flue pipe, check the chimney, and test draft, smoke and combustion efficiency. |
| Every year | Inspect the oil tank and supply line for rust, weeping or damage, and keep the tank vent and fill pipe clear. |
| Every 5–10 years | Replace CO alarms according to the date printed on them. |
Troubleshooting
Many no-heat calls come down to the thermostat, the filter or a switch. Work through the checks below, but leave gas, oil, venting and electrical repairs to a qualified technician.
| Problem | Possible cause | What to try |
|---|---|---|
| No heat | Thermostat setting or batteries; emergency switch off; empty oil tank; burner in lockout. | Check the thermostat and the emergency switch (often at the top of the basement stairs); check the tank gauge. Press the burner reset button once only — if the burner does not stay lit, call for service. |
| Burner runs but shuts off and locks out | Clogged nozzle or filter; air in the oil line; dirty cad cell; poor draft. | Do not keep resetting. Call an oil-heat technician. |
| Soot, smoke or oil smell | Poor combustion; cracked heat exchanger; draft problem; puffback. | Turn the furnace off at the emergency switch and call for service before using it again. |
| Short cycling (frequent on/off) | Dirty filter; blocked returns or registers; oversized furnace; thermostat near a heat source. | Replace the filter, open registers and clear returns. If cycling continues, have the contractor check temperature rise and sizing. |
| Status light blinking | The control board is reporting a diagnostic code. | Count the flashes and compare with the code label inside the furnace door or the code table in your manufacturer's manual. |
| Burning-dust smell at the first start of the season | Dust burning off the heat exchanger. | Normal for a short time. A persistent burning, electrical or rubber smell means shut the furnace off and call for service. |
Energy use and running costs
The examples assume a home that needs 50 million Btu of delivered heat per year — roughly a mid-size house in a cold northern climate. Scale the figures up or down for your home and climate. At 87% AFUE the Conforto KHM-G3-*078-03 would burn about 415 gallons of heating oil a year (heating oil contains roughly 138,500 Btu per gallon). An oil furnace at the federal minimum of 83% AFUE would need about 435 gallons for the same heat — 20 gallons more.
Heating-oil prices vary widely by region and season, so multiply these gallons by your local delivered price to estimate cost. The burner motor and blower also use electricity, which is not included here.
Frequently asked questions
What is the AFUE rating of the Conforto KHM-G3-*078-03?
The Conforto KHM-G3-*078-03 is rated at 87% AFUE, so about 87 cents of every fuel dollar becomes heat in your home over a typical season.
What fuel does the Conforto KHM-G3-*078-03 use?
It is an oil-fired furnace that burns heating oil from a storage tank. It requires an annual burner tune-up and a properly lined chimney or listed power-vent system.
Is the Conforto KHM-G3-*078-03 ENERGY STAR certified in northern states?
Yes. It is certified for all regions, including the northern U.S., where ENERGY STAR applies stricter requirements.
When was the Conforto KHM-G3-*078-03 ENERGY STAR certified?
It appears on the ENERGY STAR certified furnace list with a certification date of September 2026, certified for all regions.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified furnaces dataset published by the U.S. Environmental Protection Agency (record certified September 15, 2026), retrieved October 7, 2026.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Conforto. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Conforto or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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